Data storage devices employ rotating data storage media such as hard disk drives. In a hard drive, data is written to the disk medium using a write head which generates a high localized magnetic field which aligns magnetic domains within the disk in one of two directions. In some cases, the magnetization direction is up or down relative to the plane of the disk (perpendicular magnetic recording, or PMR). In other cases, the magnetization direction is within the plane of the disk. In all cases, this data may then be read-out with a read head. The write and read heads are typically integrated within a single assembly. To achieve steadily increasing data storage densities (typically measured in bits/inch2), which are now achieving levels near 1012 bits/in2, the sizes of magnetic regions storing individual bits have been reduced to nm levels.
To achieve these increasing data storage densities, the dimensions (widths) of data tracks are being steadily decreased and the track-to-track spacings also reduced correspondingly, with the result that magnetic interference effects between neighboring tracks (adjacent track interference, ATI), and nearby tracks (far track interference, FTI) are becoming an increasing problem for the maintenance of data integrity. One current solution to this problem is to monitor the total number of writes on any given track and in idle time (i.e., in periods during which the host computer is not transmitting read or write commands to the HDD), execute a background media scan. During this background media scan, lower levels for correction (i.e., fewer error-correction code bits) are used—if the track can still be read but is compromised, it is refreshed (i.e., the same data is rewritten into that same physical location on the disk medium). The time required for these data readout and rewriting operations may affect the overall performance of the HDD and is undesirable.
Thus it would be advantageous in a data storage system to provide a method for improved control of far track interference (FTI) and adjacent track interference (ATI) effects with reduced overhead on HDD operation, thereby improving the overall performance of the HDD.
It would also be advantageous to provide a method for rewriting zones closer to other zones with similar writing frequencies: cold zones near other cold zones, and hot zones near other hot zones, thereby reducing the need for FTI rewrites in both the cold and hot zones.